Combining advances in nanotechnology with molecular biology and imaging is providing exciting new nanomedicine-based strategies for cancer treatment. The ideal cancer therapy would target cancer cells while sparing normal tissue. In most conventional chemotherapies, normal cells are damaged together with cancer cells. siRNA-mediated silencing of specific targets has significant potential in cancer therapy to down-regulate pathways that are up-regulated in cancer cells but not in normal tissue to achieve cancer cell-specific treatment. Similarly, prodrug enzyme therapy, where a drug-activating enzyme delivered to the tumor converts a nontoxic prodrug to a cytotoxic drug, is being actively investigated to minimize normal tissue damage. A combination of both strategies can be exploited to enhance the effect of conventional chemotherapy against cancer cells and minimize damage to normal tissue. Imaging can play a key role in several aspects of such a treatment. Since tumor vasculature is typically heterogeneous and chaotic, the ability to image the delivery of the siRNA and the prodrug-activating enzyme within the tumor would ascertain effective delivery. Noninvasive detection of target down-regulation and visualization of the prodrug-activating enzyme could be exploited to time prodrug administration to minimize normal tissue damage. Detecting the conversion of the prodrug to the active drug within the tumor would verify that the prodrug enzyme was functional.
Prostate cancer (PC) is the second leading cause of death from cancer in men in the United States. The vast majority of men dying of PC succumb to metastatic androgen refractory disease. There is therefore a compelling need to find effective treatments for metastatic PC. In theranostics, noninvasive imaging-based detection of a target is combined with the delivery of a therapeutic payload to the target.
There still exists, therefore, a need for targeted therapy of cancers, including metastatic prostate cancer.